The parent application hereto discloses a fault detection circuit for use with multi-phase loads, such as anti-icing or deicing heaters on aircraft The there-disclosed fault detection circuit operates by comparing the voltage at the centerpoint of a reference load with the voltages at the centerpoints of the loads to be monitored.
For certain aeronautical applications, heaters are powered by 270 VDC. It would be advantageous to provide fault detection circuitry which would work in such an environment.
One object of the invention is to provide a fault detection circuit for determining the existence of a fault in any one of a plurality of loads which are supplied by a DC source.
Another object is to provide such a circuit which is highly sensitive to faults in the loads and highly insensitive to changes in the source.
A further object is to provide such a circuit which does not require the use of many conductors which must be routed out of the loads.
Still a further object is, in general, to improve on prior art circuits of this general type.
In accordance with the invention, the DC loads to be monitored are center-tapped. A reference center-tapped load is connected across the DC source and the reference centerpoint of that reference load is used as a benchmark. The voltages at the centerpoints of all the loads to be monitored are compared against the voltage of the centerpoint of the reference load. When the voltage at any centerpoint of a monitored load is substantially unequal to the voltage at the centerpoint of the reference load, this indicates a load fault.